What describes materials that do not allow electricity to flow through them?

The term that describes materials that do not allow electricity to flow through them is insulators. Insulators are characterized by their high resistance to electric current, which makes them effective at preventing the flow of electricity. This property is attributed to the structure of insulators, which inhibits the movement of free electrons that are necessary for electrical conduction. Common examples of insulators include rubber, glass, and most plastics, which are often used to encase electrical wires or components to protect against unintended current flow.

In contrast, conductors are materials that allow electricity to flow freely, while semiconductors have properties between conductors and insulators, typically allowing for controlled conduction under certain conditions. Resistors, while related to the control of electrical current, are components designed to limit the flow of electric current rather than being materials that inherently prevent electricity from flowing. Thus, insulators are the correct choice for describing materials that hinder the flow of electricity.